Sony Tablet P

When Sony announced its entry into the Android tablet game in August 2011, it showed off two devices. One was the Sony Tablet S, which made it to market a few months later. The other was the Sony Tablet P (then known as the Tablet S2), a unique folding tablet planned to be released by AT&T in time for the holidays. It didn't.

Lenovo IdeaPad U1 Hybrid

Lenovo first showed off its IdeaPad U1 concept at CES of 2010, and its hybrid concept turned a lot of heads. The device worked as a Windows notebook when docked, but its detachable screen acted as an Android tablet when used separately.

It missed its 2010 release, but popped up again at CES 2011. Who knows? Maybe we'll see it again at CES 2012.

Dell 10-inch consumer tablet

To Dell's credit, the company was one of the first major players to challenge the Apple iPad with the Android-based Streak tablet. So when it announced its plan to deliver a 10-inch Android tablet tablet for 2011, we had every reason to believe the company. Well, it produced a 10-inch Windows 7 tablet, but an Android version never made it out the door. Maybe the cardboard mock-up company reps showed off during the announcement event (shown here) should have tipped us off.

Kno tablet

Unlike most of the tablets on this list, the Kno tablet wasn't geared for consumers. Its dual-screen design was made specifically to address the need for a full-size, full color replacement for large textbooks. Unfortunately, it never happened.

In April 2011, the company decided to change direction and abandon hardware creation to focus specifically on software development.

Samsung Galaxy Tab 7 4G

During CES 2011, Samsung announced plans to release a 4G version of the 7-inch Galaxy Tab Android tablet for Verizon. Though Samsung went on to make many new versions to its Galaxy Tab line in 2011, a 4G version of this original Galaxy Tab never materialized.